Advances in microprocessor and communication technologies have opened up many opportunities for applications that go beyond the traditional ways of doing business. Electronic commerce and business-to-business transactions are now becoming popular, reaching the global markets at a fast rate. Unfortunately, while modern microprocessor systems provide users convenient and efficient methods of doing business, communicating and transacting, they are also vulnerable to unscrupulous attacks. Examples of these attacks include virus, intrusion, security breach, and tampering, to name a few. Computer security, therefore, is becoming more and more important to protect the integrity of the computer systems and increase the trust of users.
In the context of operating systems, computer security is determined initially by establishing that you are loading (or have loaded) a trustable operating system. A trustable operating system is where the user or a third party may later inspect the system and determine whether a given operating system was loaded, and if so, whether or not the system was loaded into a secure environment.
However, when booting a normal operating system it is necessary to boot a wide variety of code components. Even if you could choose what code component should be loaded, the operating system contains such an extremely large amount of code that it is difficult to establish the operating system's specific identity and whether you should choose to trust it, i.e. whether it was loaded into a secure environment.
In a multi-processor environment, it may be particularly difficult to determine whether the operating system can be trusted. This is because each of the central processing units (CPUs), or sometimes even a system device, can execute a code stream that can potentially alter and compromise the integrity of the code that was loaded. Consequently, at least at the operating system level, it is often necessary to assume that the operating system is trustworthy. Such assumptions may prove to be false and can lead to catastrophic failures in computer security.